The world of JavaScript used to be all about Node.js, but lately, Deno and Bun.js have joined the party. Each of these runtimes has its own way of doing things, focusing on performance, safety, and making developers’ lives a little bit easier.

Even though Node.js is still the primary choice for most people, Deno and Bun.js are shaking things up by rethinking some basic design ideas.

This write-up looks at how each platform is built, how they perform, and how they fit into the larger ecosystem, pointing out the pros and cons and what projects they work best for.

Node.js: The Old Reliable

Node.js came out in 2009 -It was hated back then BTW- and changed server-side JavaScript by using Chrome’s V8 engine and a design that handles many tasks at once without blocking. Its long history has built a huge library of packages (npm now has over two million), making it the default choice for many backend JavaScript projects. Node.js works well by letting developers mix and match modules from a vast collection of libraries, frameworks, and tools. Its design is great for handling tasks like APIs and real-time applications, though heavy CPU work can slow it down because it runs on a single thread.

One key feature of Node.js is that it uses CommonJS modules, though it later added support for ES Modules (ESM) to keep up with modern JavaScript. This mix sometimes makes setup a bit tricky, especially in bigger projects. By default, Node.js doesn’t restrict what your scripts can do on your system, which gives you freedom but also means you need to be careful about security. Over time, Node.js has added things like worker threads for heavy tasks and better tools for diagnosing issues, but it still sticks to many of its original design ideas from the early 2010s.

Deno: A Modern, Safer Alternative

Deno was released in 2020 by Ryan Dahl, the creator of Node.js, as a way to fix some of Node.js’s problems. It’s built on the V8 engine and written in Rust, putting a big focus on security, modern features, and simplicity. Deno uses ES Modules by default, so there’s no need for package managers like npm since you can import code straight from URLs. This makes managing dependencies more spread out, although it can create challenges with version control and working offline.

Deno’s biggest change is its security approach.

By default, Deno’s code runs in a sandbox without access to files, networks, or the system unless you explicitly allow it. This extra safety helps keep malicious code at bay, which is great if you care a lot about security.

It also has built-in support for TypeScript (so you don’t need extra tools), and its standard library is designed to be simple and secure, reducing the need for third-party packages (not more npm audit fix).

Deno even includes testing, formatting, and linting tools out of the box to simplify the development process. However, its ecosystem isn’t as big as Node.js’s

No Node Compatibility

Deno doesn’t work with npm packages by default, it can be slower to catch on. Tools exist to help with this, but Deno’s start from scratch philosophy makes sense because the whole purpose of it is to solve Node.js shortcomings.

Bun.js: A Fast and Fresh Contender

Bun.js, which came out in 2022, markets itself as a high-speed alternative to Node.js and Deno.

Instead of using V8, it uses Apple’s JavaScriptCore engine (the same one behind Safari) and focuses on speed, quick startup times, and efficient use of resources.

Its creator, Jarred Sumner, said that Bun can run some server-side tasks up to three times faster than Node.js and handles HTTP requests with less delay.

Besides speed, Bun comes with its own package manager, bundler, and test runner built-in, aiming to bring together tools that are usually spread out in the JavaScript world.

It works with both CommonJS and ES Modules, making it easier for teams coming from Node.js, without the compatibility issues seen in Deno.

Bun’s design uses Zig for low-level control over memory and system functions, which helps with optimizations like direct SQLite support. Its package manager is built to replace npm and Yarn by speeding up downloads through parallel processes and caching.

Node Compatibility

Unlike Deno, Bun embraces the npm world, so you can use existing packages without changes. This practical compatibility along with its performance boost makes Bun appealing for teams looking for improvements without a complete overhaul. On the downside, Bun is still new, so it might not be as stable for big production projects and can have some issues on Windows or in rare cases.

Performance and Trade-Offs

Speed is a big factor that sets these runtimes apart. Node.js is reliable but can be slower because of its older design and single-threaded approach. Deno might be faster in some cases thanks to its Rust-based parts and updated V8 engine, but its extra security and TypeScript features can slow it down a bit. Bun.js currently leads in benchmarks for tasks like HTTP routing, file operations, and database queries, due to its efficient JavaScriptCore engine and light system layers built with Zig.

That said, speed isn’t everything. Node.js has been imporoving over many years, so its performance is very predictable even under heavy load.

Deno’s security adds a bit of delay, but it gives you more control over what your code can do—important for apps that deal with sensitive data.

Bun’s speed does come with some risks: JavaScriptCore isn’t as tuned for server tasks as V8, and since Bun is evolving quickly, there might be breaking changes. Developers need to consider these factors based on their project needs—teams working on low-latency microservices might lean towards Bun, while those with long-term, complex projects might stick with Node.js.

Ecosystem and Community

Node.js’s ecosystem is huge, with popular tools like Express, NestJS, and React built on it. This large community means that switching to another runtime can be a big job for large projects.

Deno’s ecosystem is still growing, and while it has a solid standard library and some third-party modules that focus on security and simplicity

Bun, on the other hand, is designed to work with npm, so you get immediate access to Node.js’s package collection along with its speed boost.

Community support also plays a big role. Node.js has a massive community that continually improves it.

Deno is mostly driven by one company, which helps keep its vision clear but might slow down adding new features.

Bun’s open-source nature and fast updates attract developers who like to experiment, though its long-term success will depend on keeping contributors engaged and getting support from larger companies.

Security and Developer Experience

Each runtime has a different approach to security. Node.js trusts the code by default, so developers have to be careful and check their dependencies to avoid issues like dependency hijacking. Deno flips the script by denying access by default—your code won’t have file, network, or environment access unless you explicitly allow it. This makes it safer but can slow down some workflows. Bun, staying close to Node.js for compatibility, uses a similar security model, though future updates might add more safety features.

When it comes to how developers work, the differences show too. Deno’s all-in-one toolchain cuts down on setup time, offering built-in testing and formatting similar to what you might find in Rust or Go. Bun’s built-in bundler and package manager speed up project setup, while Node.js relies on a variety of external tools (like Webpack or Jest) that, while powerful, add extra layers of complexity. TypeScript is another good example: Deno handles it out of the box, Node.js needs extra tools, and Bun makes it very fast by optimizing it through JavaScriptCore.

Conclusion: Picking the Right Tool

Each of these runtimes has its own strengths. Node.js is still the safest bet for big companies that need stability, a huge library of tools, and proven scalability. Deno is attractive for developers who value security, modern tools, and TypeScript-first workflows—especially in new projects or areas where safety is a top concern. Bun.js, although still new, offers impressive speed and a simplified toolchain for teams ready to work with a rapidly evolving platform.

The future of JavaScript runtimes isn’t about one completely replacing the others but about all of them evolving together. Node.js is adding new features like WebAssembly support, Deno is finding its place in enterprise settings, and Bun.js is sharpening its performance edge. When choosing between them, consider your project’s lifespan, speed needs, and how much risk you’re willing to take. As the JavaScript world grows, we might see more overlap and mixing of these ideas, but for now, each runtime has its own place in the scene.

This article was written by Ahmad Adel. Ahmad is a freelance writer and also a backend developer.